Crystal Structures, EPR Spectra, and Magnetic Properties of a Series of Ionic Multi‐Component Complexes [(TBPDA)2·(C60·–)·(D+)] (D = Cp*2Cr, Cp*2Co, TDAE)

Abstract

AbstractNew ionic multi‐component complexes [(TBPDA)2·(C60·–)·(D+)] [TBPDA = N,N,N′,N′‐tetrabenzyl‐p‐phenylenediamine; D = decamethylchromocene (Cp*2Cr, 1) and decamethylcobaltocene (Cp*2Co, 2)] were obtained additionally to previously characterized [(TBPDA)2·(C60·–)·(TDAE·+)] [TDAE = tetrakis(dimethylamino)ethylene, 3]. The presence of D+, C60·–, and neutral TBPDA in 1–3 was proved by the IR and UV/Visible/NIR spectra. D+ and C60·– form loose layers in 1 and 3 and are spatially separated by bulky TBPDA molecules. The C60·– radical anions alternate in the layer with the phenylene groups of TBPDA to form π‐π stacking, whereas disordered Cp*2Cr+ cations are isolated in the voids formed by eight benzyl groups of TBPDA. The EPR spectra of the complexes show single Lorentzian lines with g = 2.2526 and ΔH = 215 mT (1), g = 1.9999 and ΔH = 6.7 mT (2), and g = 2.0009 and ΔH = 2.93 mT (3) at room temperature. The EPR signal of 2 was attributed to C60·– (Cp*2Co+ is diamagnetic) and those in 1 and 3 to resonating signals between C60·– (g = 1.9996–2.0000) and Cp*2Cr+ [an asymmetric EPR signal with g[perp] = 4.02(1) and g[par] = 2.001(1)] (1) or TDAE·+ (g = 2.0035; 3) due to indirect coupling. The EPR signals from 2 and 3 are split into two components below 50 and 60 K, respectively, which shift in the opposite directions (to lower and higher fields) with decreasing temperature. The magnetic moments of 1–3 decrease below 50–100 K. Both effects are associated with the formation of field‐induced short‐range antiferromagnetically ordered clusters. It is shown that the D+ cations do not noticeably affect this interaction. Most probably, it is realized mainly between C60·– spins within the layer and is mediated by the phenylene groups of TBPDA. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)